my goldfish has spots of brown on his body. it's not changing color, if it were it would be darker, more dense, and more concentrated. and it's not velvet disease. if it were it would look like red dust, and again would be more concentrated. it's on his snout, fins, one gill cover, and a few of his scales. it's about the color of the algae that grow in my tank. it's not algae! algae don't grow on fish.